Alkylation of aromatic hydrocarbons with selective isomers and homologs



United States Patent O ALKYLATION F AROMATIC HYDROCARBONS WITH SELECTIVE ISOlVIERS AND I-IOMOLOGS George L. Hervert, Downers Grove, and Herman S. Bloch, Chicago, Ill., as'signors to Universal Gil Prodn ucts Company, Des Plaines, Ill., a corporation of Delaware Application December 18, 1953, Serial No. 398,948

9 Claims. (Cl. 260--671) `alkyla-tes, particularly ythe alkylates of benzene containing relatively long chain alkyl groups especially useful as intermediates in production of alkylaromatic sulfonate detergents. More specifically, the present invention concerns a process for producing aromatic hydrocarbon alkylates utilizing an alkylating agent comprising a mixture of isomeric and homologous oleiinic hydrocarbons of varying reactivity with the aromatic charging stock in the presence of an alkylation catalyst, in which process the sulfuric 'acid utilized as alkylation catalyst is initially contacted with the mixture of alkylating agents and the resulting extracted components condensed with Ian Iaromatic hydrocarbon `at relatively mild alkylation reaction conditions while the non-extracted components of the mixture of alkylating agents are contacted with the same or a different aromatic hydrocarbon in the presence of sulfuric acid as .the alkylation catalyst at alkylation reaction conditions relatively more severe than in the rst mentioned alkylation reaction.

An object of this invention is to provide a process for the alkylation of aromatic hydrocarbons in which the yield of alkylate per unit weight of alkylating agent charged to the reaction is greater 'than in the conventional single stage alkylation reaction. Another object of the invention is to increase the yield `of `desired alkylate formed in a given alkylation reaction involving an aromatic hydrocarbon as one of the reactants and a mixture of isomeric and homologous olenic hydrocarbons as the al-kylating agent to thereby reduce the cost of the -alkylate on the basis of the quantity of lalkylating agent and catalyst charged to the reaction. Still another object of the invention is to provide an alkylation process in which a greater proportion of the yield of product corresponds to an alkylate of a particularly desirable structure, substantially free of multiple alkyl-substituted products and depolyalkylate.

lIn one of its embodiments the present invention concerns an improvement in the process for alkylating an aromatic hydrocarbon wit-h a mixture of isomeric loletinic hydrocarbon alkylatin-g agents which comprises contacting said mixture comprising straight chain and branched chain `oleiin isomers with sulfuric acid of from about 80 to about 95% concentration to form a rainate comprising straight chain olens and an extract comprising said acid and branched chain olelins, separating said extract from the raffinate and adding an aromatic hydrocarbon thereto, subjecting the resultant mixture to alkylating conditions to react said aromatic hydrocarbon and branched Vchain oleiins in the presence of said sulfuric acid as alkylation catalyst, commingling said raiiinate with additional aromatic hydrocarbon and sulfuric acid of greater concentration than .the acid supplied to said contacting step,

.subjecting the mixture thus formed to alkylating condi- ICC tions to react said additional aromatic hydrocarbon with straight chain olens .contained in said rainate, separating the acid phase from the resultant products and supplying at least a portion thereof to .the iirst mentioned alkylating step to fortify the catalytic activity of the sulfuric acid contained in said extract.

Other embodiments relating to more speciic aspects of the present invention, su-ch as the number of carbon atoms in the oleiinic mixture and the aromatic hydrocarbon employed in each of the first mentioned tand second mentioned alkylation steps will be referred to in greater detail in the following further description of the invention.`

Of the alkylatable aromatic hydrocarbons utilizable in the present alkylation process, that is, of the aromatic hydrocarbons containing a nuclearly displaceable hydrogen atom which is replaceable by an alkyl group in the presence of a suitablealkylation catalyst, benzene is generally considered to be one of the most refractory and diicult to alkylate in appreciable yields of alkylate product. Depolymerization and hydrogen transfer reactions are especially pronounced and evident in the alkylation of benzene with relatively long chain olens which contain tertiary or quaternary ethylenic carbon atoms in the structure of the olefin; the olens containing di-alkyl substituted ethylenic carbon atoms are particularly subject vto hydrogen transfer reactions in the presence of acidic catalysts normally used in the alkylation of benzene. A relatively large proportion of the polymers, saturated parainic hydrocarbons (formed by virtue of the hydrogen transfer reactions), lower alkylbenzenes and other diverse undesirable products. It has now been discovered that in alkylation reactions in which an Iaromatic hydrocarbon, and particularly benzene is an alkylation reactant and a branched chain olenic hydrocarbon or a mixture of isomeric -olefins of a particular molecular weight are utilized as alkylating agent, the oletns which lare branched chain in structure may be selectively extracted from the relatively more straight cha-in isomers and homologs in the mixture by contacting the same with sulfuric acid lof a specic range of concentration. Furthermore, the extract thus produced comprising the sulfuric acid extractant and the relatively branched chain olen isomers may be utilized directly or with the addition thereto of more concentrated sulfuric acid to alkylate an aromatic hydrocarbon at relatively mild reaction conditions as compared to the reaction conditions required Vfor the condensation of the aromatic charging stock with the non-extracted, relatively Istraig-ht chain .components of the oleiinic mixture. The oleiinic components which'are relatively more resistant to sulfuric acid extraction and which resist the various indicated side reactions occurring during the alkylation reaction, that is, the Lrelatively straight chain isomers, may be separately reacted with benzene at relatively more severe reaction conditions to form an additional yield of alkylate which may be combined with the alkylfate formed by the condensation of benzene with the sulfuric acid-extracted oleinic components of the mixture. It is thus possible by means of the present two-stage alkylation' process in combination with a preliminary extraction stage, to increase the yield 'of alkyla-te from a given quantity of oleiins by decreasing the proportion of the undesirable by-products formed from the more highly branched chain olefin -isomers of the alkylating agent through separate condensation of the extracted and non-extracted portions of the olefin-ic feed stock with benzene at conditions selective for the particular olefin isomers or aromatic hydrocarbon involved in the separate alkylaticn stages.

Benzene in its pure form or as a benzene concentrate containing at least 30% by weight of benzene, separated, for example, as an appropriately boiling fraction from crude petroleum or a petroleum conversion product such as a reformed and dehydrogenated methylcyclopentanecyclohexane fraction of petroleum, may be utilized as the source of the benzene reactant in the alkylation process. The aromatic hydrocarbon charging stock utilized in the second stage alkylation reaction may be of the same or of a different species of aromatic hydrocarbon than the aromatic charging stock to the fiirst stage alkylation reaction, but in the lit-rst stage is preferably a species which alkylates more readily with the more highly branched olefinic hydrocarbon than the aromatic species utilized lin the second stage reaction. Thus, the more readily alkylatable aromatic hydrocarbon charging stock to the tirst stage alkylation reaction may be a monoor a dialkyl aromatic hydrocarbon, such as toluene, a xylene isomer, ethyl toluene, a methyl naphthalene, a dimethyl naphthalene, a methyl-ethyl-naplrthalene, diphenyl or other alkylatable hydrocarbon containing a `tlisplace'able nuclear hydrogen atom subject to alkylation. It is to be emphasized, however, that any aromatic hydrocarbon species may be u'tilized in either the .first or second stage or the same aromatic charging stock may be employed in both stages of the process, although the present arrangement of process flow is particularly advantageous when utilizing toluene in the first stage and a less readily alkylatable hydrocarbon such as benzene in the second stage alkylation reaction at more severe reaction conditions or in the presence of a more catalytically active sulfuric acid catalyst.

The long chain olefinic hydrocarbon alkylating agents utilized in the present process to form aromatic hydrocarbon alkylates normally occur in the form of mixtures of isomers and homologs boiling over a relatively narrow range and generally occur as difiicultly separable fractions, for example, as an azeotropic mixture derived from the product of a petroleum conversion process. Of Ithe various possible isomers which a given mixture of olefinic hydrocarbons may comprise, the group referred -to herein as the straight chain components having the following structure: RCH=CH2 and RHCICHR, in which R and R' are alkyl radicals, form secondary lalkyl sulfates Iby yreaction with sulfuric acid which proceeds only at relatively severe reaction conditions. Other isomeric components which `are present in 'a mixture or fraction of long chain oletinic hydrocarbons, and which `are referred to herein as branched chain components are of the followand form tertiary alkyl sulfates when contacted with sulfuric acid; the latter reaction, however, proceeds more readily at relatively mild reaction conditions. The former, less readily sulfated olenic isomers are also referred to as unsubstituted ethylenes, while the latter group which form sulfates at relatively mild conditions may lalso be referred to as alkyl-substituted ethylenes in which the alkyl group is attached to one or both of the carbon atoms of the ethylenic linkage. It is evident that the number of possible isomers of a given class of compounds increases rapidly -as the molecular weight of the compound increases. It has also been discovered that certain components of a mixture of isomeric oleiins having a .given molecular weight are more readily condensable with an aromatic hydrocarbon than other components of "the same mixture and that these more readily condensable components are likewise the most easily extracted from the mixture with an extracting agent comprising lsulfuric acid. It is thus characteristic of such more readily extracted components that they may be condensed with an aromatic hydrocarbon which is more diflcult to lalkylate or in the presence of a catalyst of lesser activity or at less severe reaction conditions, such as at a Cil lower reaction temperature, than the components of the mixture of isomers not extracted from the mixture with sulfuric acid. It has been observed, for example, that in a mixture of propylene polymer isomers, such `as a C9 to C15 fraction thereof, the portion of the mixture which is soluble -in a dilute sulfuric acid extractant is capable of alkylating benzene at a lower reaction temperature and in the presence of a weaker or more dilute hydrocarbon catalyst than the portion of the mixture of polymers not initially soluble lin the sulfuric acid extractant; whereas, if the entire polymer fraction is used in a one-stage alkylation reaction under conditions severe enough to give relatively complete conversion, the easily extractable, more highly branched isomers undergo extensive side-reaction.

Therefore, when combined with a succession of at least two alkylation reaction stages, the extracted olefinic hydrocarbon component may be utilized to alkylate rbenzene or a more readily alkylatable aromatic such as toluene under relatively mild conditions, while the non-extracted components may be diverted into a secondary alkylation stage to alkylate benzene or toluene at relatively more severe reaction conditions. Although particularly applicable in a process in ywhich .the charging stock to the initial lalkylation reaction is benzene, the present process may 'also be applied with equally advantageous and effective results when the aromatic charging stock to the initial or second stage -alkylation reaction is another aromatic hydrocarbon species, such as toluene, xylene, naphthalene, alkylnaphthalenes, etc., or a non-hydrocarbon aromatic such as phenol.

Of the alkylating agents utilizable in the present invention, the olelinic hydrocarbons containing at least four carbon atoms per molecule, and preferably containing from about 9 to about 18 carbon atoms per molecule for the manufacture of detergent alkylate, are particularly adapted to the present combination proces. Such oletinic hydrocarbon alkylating agents may be derived, for example, from the dehydration products of alcohols of similar chain length, the dehydrohalogenation products of an alkylhalide, appropriately boiling fractions of cracked petroleum products, such as a thermally cracked pressure distillate fraction, a mixture of polymers of a lower molecular weight olefin, such as a propylene and/ or butylene polymer fraction, and from other sources well known in the art.

In the production of detergent alkylate for the manufacture of the corresponding alkali metal sulfate salts, oletinic hydrocarbon alkylating agents containing from about 9 to about 18 carbon atoms, and preferably from about l2 to about 1S carbon atoms per molecule are generally preferred when alkylating a benzenoid aromatic hydrocarbon, while alkylating agents containing from about 6 to about 9 carbon atoms per molecule are preferred when alkylating a polycyclic aromatic hydrocarbon. Propylene polymer alkylating agents yield particularly desirably alkylates for detergent manufacture.

The extracting agent utilized in the initial stage of the present combination process and which may serve as the sole source of alkylating catalyst in the initial alkylation stage comprises sulfuric acid containing 'from about SO to about 95% sulfuric acid and preferably from about to about 90% sulfuric acid. In accordance with the present preferred method of effecting the two-stage alkylation process, sulfuric acid of relatively high concentration is fed ,into the secondary stage alkylation reaction to effect the condensation of the least readily condensable isomeric oleiinic components of the mixture of alkylating agents charged to the process with an aromatic hydrocarbon which may be benzene, a relatively refractory alkyl acceptor. The resulting used catalyst phase is separated from the hydrocarbon layer formed in the alkylation reaction and utilized, after fortification with addi-tional sulfuric acid of greater concentration, as the condensation catalyst in the iirst-stage alkylation reaction, or diluted with water if necessary and used as the extracting The alkylation catalyst for the primary and secondary j :alkylation reactions of the present combination process is sulfuric acid of suiiicient concentration to effect condensation of the alkylating agent with the aromatic hydrocarbon charged to the respective alkylation stages.

The alkylation catalyst utilized in the first stage alkylation reaction consists at least in part of the sulfuric acid extractant employed in the preceding extraction stage and may be additionally fortified with more concentrated sulfuric acid, sulfur trioxide, or chlorsulfonic acidl to increase the strength of `the sulfuric acid in the extract to a concentration sufficient to effect condensation of the aromatic hydrocarbon with the lextracted olefinic hydrocarbon contained in the extract phase. It is to be noted, however, that it is not necessarily essential to increase the strength of the sulfuric acid contained in the extract phase in order for the acid to have catalytic activity in alkylating the aromatic hydrocarbon charging stock, particularly when the sulfuric acid utilized as extractant is a relatively concentrated acid, containing, for example,

from about 90 to about 95% sulfuric acid, or if the arojf matic charging stock to the first stage alkylation reaction is a readily alkylatable aromatic hydrocarbon, such as toluene, xylene, methyl naphthalene, etc. The sulfuric acid catalyst utilized in the second stage alkylation reaction wherein the aromatic hydrocarbon charging stock is contacted with the least readily alkylatable isomers of the olefinic hydrocarbon mixture charged to the extraction stage of the process is a relatively active alkylation lcatalyst, such as concentrated sulfuric acid having a concentration of at least 90% acid, and preferably having,.

a concentration of from about 93 to about 99% sulfuric acid. The used acid catalyst phase from the secondary alkylation reaction may be transferred in part or in whole to the primary alkylation reaction stage and mixed therein with the sulfuric acid extract recovered from they@ extraction stage of the process as the catalyst to effect alkylation of the aromatic hydrocarbon charged thereto and the extracted isomers from the mixture of isomeric and homologous olefins initially charged to the process.

The extraction stage of the process which is effect'edgf,

by contacting the mixture of isomeric and homologous olefins with a relatively dilute sulfuric acid, containing, for example, from about 80 to about 95 and preferably from about 80 to about 90% sulfuric acid, may be accomplished by thoroughly mixing the olefinic charge;55

stock with the sulfuric acid extractant in a Volume ratio of the extractant to the mixture of olefins of from about 0.1:1 to about 5:1 volume proportions at a temperature of from about 20 to about 50 C. -Inv the first stage alkylation reaction, the condensation of an aro-(,160

matic hydrocarbon with the olen acid esters present in the sulfuric acid extract phase recovered from the extraction column is effected at a temperature of from about '-30 to about 30 C., preferably from about 0 to about 20 C. In order to obtain the desired mono-fT alkyl substituted aromatic alkylate, it is desirable to maintain the proportion of aromatic hydrocarbon to olefinic feed stock at a relatively high value, preferably from about 2:1 to about 10:1 molar proportions. The alkylationreaction may be catalyzed entirely by the sul-i furic acid present in the extract phase recovered from the extraction step, or additional sulfuric acid of the same or greater concentration may be introduced into the first stage alkylation reactor to promote the rate -.of reaction. Itis to be noted that when utilizing the vrelatively dilute sulfuric acid present in the extract phase as the sole first-stage alkylation catalyst, the reaction conditions provided in the alkylation reactor are desirably maintained at a higher temperature level and/ or the time of contact is prolonged to enhance the yield of alkylate product. The second stage alkylation reaction wherein an aromatic hydrocarbon is condensed with the rainate olefins recovered as the acid-insoluble phase of the extraction stage of the present process is effected in the presence of sulfuric acid containing not more than about 7% water at temperatures of from about 30 to 30 C., preferably from about 0 to about 20 C., utilizing a ratio of aromatic hydrocarbon to olens of from 1:1 to about 20:1 molar proportions. The used acid phase recovered from the second stage alkylation reaction is utilized as the fortifying acid charged into the first stage alkylation reactor.

The present invention is further described and illustrated with respect to one of the preferred specific embodiments thereof in the following description ofthe accompanying diagrammatic drawing which illustrates the present combination process as applied to the use of a mixture of propylene polymer isomersas the alkylating agent, a countercurrent extraction apparatus for separating the more readily alkylated isomers from the more refractory components of the mixture of propylene polymers, the use of toluene in the first stage alkylation reactor to combine with the more readily alkylatable olelinic components of the mixture of propylene polymers and the use of benzene as the aromatic hydrocarbon charge stock in the second stage alkylation reaction to ycondense the benzene with the more refractory compo! nents of the mixture of propylene polymer isomers.

Referring to the drawing, the mixture of propylene polymers utilized as the alkylating agent and consisting of various isomeric and homologous oleiinic hydrocarbons is introduced into the process flow through line 1, containing valve 2 and is preferably charged into the bottom portion of a vertical countercurrent extraction unit which may consist of a packed vertical column for obtaining more intimate contact between the extracting agent and hydrocarbon mixture or may consist of a vertical column containing horizontally disposed bubble cap trays for intimately contacting the mixed olefin polymers with the sulfuric acid extractant. The mixture of propylene polymers flows upwardly through the column against a downwardlyy owing stream of sulfuric acid extractant introduced through line 4 near the top of extraction column 3. The latter may be fresh extractant introduced from storage and containing from 80 to 95% sulfuric acid or may be spent sulfuric acid alkylation acid derived from subsequent stages of the present combination process, as hereinafter described. The olenic, isomeric components of the alkylating agent dissolving in the sulfuric acid extractant form mixtures of olefin acid sulfates which are removed from the bottom of extraction column 3 through line 5 containing valve 6 and pump 7 which transfers the acid extractant and the olefin acid sulfates contained therein through line 8, into the first stage alkylation reactor 9 wherein the olefin acid esters are reacted with toluene to form the corresponding toluene alkylate as hereinafter more fully described. The olefinic components of the mixture of propylene polymer alkylating agents which fail to dissolve in the sulfuric acid extractant in column 3 and which constitute the olefin isomers of lesser alkylating activity are removed from the upper portion of the extraction column 3 through line 10 containing valve 11 and pump 12 which transfer the most refractory olefinic components through line 13 into alkylating reactor 14 wherein the olens are contacted with a less readily alkylatable aromatic hydrocarbon such as benzene, the ensuing alkylation being effected at relatively more severe reaction conditions in the case of benzene than v for toluene. Benzene introduced into the process for this 7 valve 16, 'desirably in at least equimolar proportions with the ol'ein'ic alkylating agent and preferably in a molar proportion of from about 1:1 to about 10:1 moles of benzene per mole of olenic hydrocarbon contained 1n the raiinate from extraction column 3.` Fresh sulfuric acid containing not more than about 7% by weight of water is introduced into the alkylation reactor 14 through line 17 containing valve 18 in an amount suicient to provide an acid to hydrocarbon ratio of from about 0.1 to about 2:1 weight proportions in the reactor. Alkylation reactor 14 is preferably a stirred pressure autoclave in which the pressure is maintained at a value sufficient to maintain the reactants in substantially liquid phase during the alkylation reaction.

Following a residence time i'n the reactor of at least ten minutes, and preferably from about 1/3 to about 2 hours in duration, the contents of reactor 14 are removed therefrom through line 19, valve 20, and pump 21 which transfers the reaction mixture through line 22, emptying into line 23, through valve 24 and into settler 25 wherein an acid phase is allowed to separate from the hydrocarbon product comprising alkylate and unreacted hydrocarbon feed stock. After separating from the acid phase by settling, the latter hydrocarbon layer is removed from settler 25 through line 26 containing valve 27 by means of pump 2S which transfers the hydrocarbon product into line 29 leading to hydrocarbon Washing and fractionating units, not illustrated on the accompanying diagram. The acid phase separating from the hydrocarbon layer in settler 2S as the more dense layer therein, is removed from the settler through line 30 containing valves 31 and 32 and discharged from the process, or recycled in part (by means not shown in the illustration) to reactor 14, or is preferably diverted at least in part into line 33 through pump 34 which transfers the acid alkylation sludge into line 35 and into alkylation reactor 9 wherein the spent acid is utilized to fortify the catalyzing activity of the sulfuric acid in the extract phase recovered from extraction column 3. The olens contained in the extract phase from column 3 which alkylate aromatics more readily than the ranate olens utilized in reactor 14 are introduced into alkylation reactor 9 through line 8, as aforesaid, and toluene is admitted into reactor 9 through line 36 and valve 37.

In order to promote the alkylation reaction in reactor 9 and enhance the yield of alkylate product, sulfuric acid of either the same or greater concentration as the acid comprising the extract phase may be added to the latter stream as it iiows into reactor 9 through line 38 containing valve 39, the acid being introduced into the flow by connection of line 38 with line 8, the amount being adjusted to provide the optimum ratio of acid to hydrocarbon phase in the alkylation reaction mixture.

The alkylation reaction products of reactor 9 are removed therefrom through line 40 containing valve 41 and pump 42 which discharges the 'mixture of spent acid and hydrocarbon products as well as unreacted charging stock into line 43 connecting with line 44 containing valves 45 and 57 which control the flow of alkylation reaction mixture either into settler 46 or into line 44 leading via line 23 into settler v2S. The alkylation reaction mixture from reactor 9 may be transferred to settler 25 and thereby utilized in common with the reaction mixture from reactor 14 to separate the spent acid layer from the hydrocarbon layer produced in the alkylation reaction. If, on the other hand, it is preferred to 'separately treat the alkylation reaction mixtures from reactors 9 and 14 in order to recover the respective acid and hydrocarbon phases, valve 57 in line 44 is closed and valve 45 in line 44 is opened, the alkylation reaction mixture from reactor 9 thereby being pumped by means of pump 42 into settler 46 wherein the hydrocarbon and acid layers are allowed to separate. In the latter procedure, the hydrocarbon layer separating from .the acid layer, is an upper phase in 'settler 46 and is removed therefrom through line 47 containing valve 48 by means of pump 49 which discharges the hydrocarbons into line 50 connecting with washing and fractionating apparatus, not illustrated on the accompanying diagram, for separating desired alkylate from unreacted charging stock. The acid phase separating in settler 46 is removed through line 51 containing valves 52 and 53 which control the flow of the spent acid sludge either into a waste disposal unit, not illustrated on the accompanying diagram or to partial recycle to reactor 9 (by means also not shown), or by closing valve 53, lthe spent acid is diverted into line 55 by means of 'pump 54 which circulates the acid into line 56 connecting line 4 therewith for use of the acid as the extrac'tant in extraction vessel 3.

The alkylation reaction mixture removed from alkylation reactor 14 through line 19, valve 20, and pump 21 may alternatively be diverted into settler 46 by closing valve 24, thereby directing the mixture into line 44, through valves 57 and 45 into settler 46. In the latter alternative process ow, the alkylation mixture from reactor 14 is mixed with the alkylation mixture from reactor 9 and the combined products allowed to settle in vessel 46. The mixing of the alkylate products from both reactors 9 and 14 is especially advantageous when the aromatic hydrocarbon charging stock to both reactors is the same, as in the case when either benzene or toluene is charged into both reactors as the aromatic hydrocarbon reactant. Where the aromatic hydrocarbons charged into reactors 9 and .14 are different, it is generally preferable to settle the reaction mixture in separate settlers, as indicated by settlers 25 and 46 respectively, although in the case vof the alkyl benzene and alkyl 'toluene sulfonate detergents, a product comprising a mixture of said sulfonates is an effective detergent mixture and may be utilized when desired.

The present invention is further illustrated with respect to specific embodiments thereof in the following examples, which, however, are not to be considered as limiting the generally broad scope of the invention in strict accordance therewith.

Example I A mixture of propylene polymers fractionated from the high boiling ends of a propylene-propane polymerization product, boiling from about 170 to 225 C. and consisting of various C11, C12, and C13 propylene polymer isomers, about 85% of which consists of a mixture of C12 isomers comprising monoalkyl, dialkyl, trialkyl, and tetra-alkyl-ethylenes is mixed with 0.7 volume proportions of 94% sulfuric acid at a temperature of from about 10 to about 25 C. under vigorous stirring conditions suicie'ntto distribute the acid in finely divided droplets throughout the hydrocarbon mixture. The resulting acidhydrocarbon mixture is thereafter allowed to settle and to stratify into an upper hydrocarbon phase and a lower acid extract phase, the resulting phases being separated by decantation. As a result of the sulfuric acid extraction, the rainate hydrocarbon, upper phase has decreased from 1.0 volume to 0.78 volume, while the acid phase has increased in volume from 0.7 to 0.85 volume.

The acid phase containing extracted olenic components from the mixture initially subjected to extraction is thereafter mixed with 10volume proportions of benzene based upon the quantity of olefins contained in the acid extract phase, that is, the decrease in volume of the olefin phase (or, 10 0.22=2.2 volumes) at 0 C. The resulting alkylation reaction mixture is stirred at the above temperature for a reaction period of minutes at a stirring rate su'licient to thoroughly mix the hydrocarbon and acid phases. The resulting alkylation reaction mixture is thereafter allowed'to stratify, forming an upper alkylate layer and `a lower acid sludge layer which latter layer is discarded from the process. The upper alkylateilayer is washed with caustic-and then fractionated to recover benzene, unreacted olens,and analkylate fraction lboiling from 275 to 325 C. containing the desired dodecylbenzene in a yield of 65% of theoretical, lbased upon the quantity of olens contained in the sulfuric acid extract phase.

The olefinic hydrocarbon raffinate separated as the acid-insoluble phase in the initial sulfuric acid extraction procedure, containing olenic hydrocarbons which resist dissolution in the sulfuric acid extractant and which represent about 78 volume per cent of the original olefmic charging stock mixture subjected to extraction is mixed with l volume proportions of benzene (7.8 volumes, based upon the initial charge of olenic hydrocarbon) and with 2.5 volumes of 98.5% sulfuric acid based upon the total volume of olenic hydrocarbon rainate. The hydrocarbon-acid mixture is thereafter stirred at a temperature of C. for a reaction period of 40 minutes. Following the indicated period of reaction, the mixture is allowed to stand quiescent until phase separation occurs in which an upper essentially hydrocarbon phase separates from a lower acid phase, the latter being decanted and reserved for use in the extraction of the initial oleiinic hydrocarbon charging stock. The upper hydrocarbon layer is separated from the acid sludge layer, washed with water to remove residual acid therefrom, dried, and fractionally distilled to separate a secondstage alkylation product fraction boiling from 270 to 325 C., comprising principally dodecylbenzene. The yield of the latter alkylate product based upon the quantity of olefinic hydrocarbons subjected to alkylation, that is, based upon 0.78 volume of olefinic raffinate subjected to alkylation, is S0 mol per cent.

The desired alkylate product from the first and second stage alkylation reactions, comprising the 275-325" C. fractions of the respective hydrocarbon layers recovered from the alkylation reaction mixtures in the irst and second stage reactions are combined and based upon the initial volume of olenic hydrocarbon charging stock charged to the extraction stage of the process, the yield of combined alkylate is 77 mol per cent, based upon the total volume of oleiinic hydrocarbons charged to the reaction.

In a similar alkylation reaction in which one volume of the total olenic hydrocarbon charging stock is subjected to alkylation with 10 volumes of benzene in the presence of 98.5% sulfuric acid at a temperature of 0 C. and for a reaction time of 80 minut-es, under vigorous stirring conditions, the yield of total alkylate based upon the olenic hydrocarbon charge to the reaction is 69.5 mol per cent. The recovered acid sludge phase from the latter reaction contains an excessive amount of hydrocarbon material, indicating incomplete utilization of the feed stock for the desired reaction.

Example 1I In an alkylation reaction in which the secondary alkylation stage utilizing the rafnate hydrocarbons which fail to dissolve in the sulfuric acid extractant, is eiected at a temperature of 10 C. rather than at a temperature of 0 C., as utilized in Example I, above, but with the other reaction conditions similar to those employed in the secondary alkylation reaction of Example I above, the yield of secondary alkylate is 82 mol per cent as compared to the 80 mol per cent yield of Example I above.

Example III In an extraction-alkylation process utilizing toluene in place of benzene as the aromatic hydrocarbon charged to the primary stage of the process, with l0 volume proportions of toluene per volume of olenic hydrocarbons contained in the extract phase of the sulfuric acid extraction stage of the process, and utilizing 0.7 volume of 94% sulfuric acid based upon the volume of oleiinic hydrocarbons subjected to extraction, alkylation at a temperature of 0 C. and for a reaction time of 81 minutes, with subsequent separation of the 275-325 C.

10 fractions from the alkylation products showed a yield of dodecyltoluene of 89 mol per cent, based on the amount of dodecylenes extracted.

We claim as our invention:

l. A process which comprises contacting a mixture of straight chain and branched chain olen hydrocarbons with sulfuric acid of from about to about 95% concentration to form a rainate comprising straight chain olens and an extract comprising said acid and branched chain olefms, separating said extract from the rafnate and adding an aromatic hydrocarbon to the extract, subjecting the resultant mixture to alkylating conditions to react said aromatic hydrocarbon and branched chain oletins in the presence of said sulfuric acid as alkylation catalyst, commingling said raiinate with additional aromatic hydrocarbon and sulfuric acid of greater concentration than the acid supplied to said contacting step, subjecting the mixture thus formed to alkylating conditions to react said additional aromatic hydrocarbon with straight chain olens contained in said raflinate, separating the acid phase from the products of the last-mentionel alkylating step and supplying at least a portion thereof to the tirst mentioned alkylating step to fortify the catalytic activity of the sulfuric acid contained in said extract.

2. The process of claim l further characterized in that said olens contain from about 9 to about 18 carbon atoms per molecule.

3. The process of claim l further characterized in that said mixture of olens is a propylene polymer fraction.

4. The process of claim l further characterized in that at least one of the aromatic hydrocarbons, subjected to alkylation is benzene.

5. The process of claim l further characterized in that the first mentioned aromatic hydrocarbon is toluene and the second mentioned aromatic hydrocarbon is benzene.

6. The process of claim l further characterized in that said sulfuric acid of from about 80 to about 95% concentration contacted with said mixture of straight chain and branched chain olens is made up at least in part from the acid separated from the products of said second mentioned alkylation step.

7. A process which comprises contacting a mixture of straight chain and branched chain olen hydrocarbons with sulfuric acid of from about 80 to about 95 concentration to separate branched chain olens from straight chain olens, alkylating an aromatic hydrocarbon with thus separated branched chain olens in tne presence of sulfuric acid catalyst comprising used acid from said contacting step, and separately alkylating additional aromatic hydrocarbon with separated straight chain olens from the contacting step in the presence of sulfuric acid catalyst of higher acid concentration than the catalyst present in the first-mentioned alkylating step.

8. A process which comprises contacting a mixture of straight chain and branched chain olefin hydrocarbons. with sulfuric acid of from about 80 to about 95% conccn` tration to form a rafiinate comprising straight chain olens and an extract comprising said acid and branched chain olefins, separating said extract from the ranate, commingling an aromatic hydrocarbon with the extract and alkylating the same with the branched chain oleiins in the presence of sulfuric acid catalyst comprising the, acid component of the extract, and separately alkylating additional aromatic hydrocarbon with the straight chain olefin content of said raflinate in the presence of sulfuric acid catalyst of higher acid concentration than the catalyst present in the rst-mentioned alkylating step.

9. A process which comprises contacting a mixture of straight chain and branched chain olefin hydrocarbons with sulfuric acid of from about 80 to about 95 concentration to separate branched chain olefins from straight chain olefins, alkylating an aromatic hydrocarbon with thus separated branched chain olens in the presence of a relatively mild sulfuric acid catalyst comprising used acid from said contacting step, separately alkylating additional aromatic hydrocarbon with separated straight chain oleus from the contacting step in the presence of sulfuric acid catalyst of higher acid concentration than the first-mentioned catalyst, separating the acid phase from the products of the last-mentioned alkylating step and supplying at least a portion thereof to the rstamentioned alkylating step to constitute a part of said relatively mild sulfuric acid catalyst.

References Cited in the le of this patent UNITED STATES PATENTS 

1. A PROCESS WHICH COMPRISES CONTACTING A MIXTURE OF STRAIGHT CHAIN AND BRANCHED CHAIN OLEFIN HYDROCARBONS WITH SULFURIC ACID OF FROM ABOUT 80 TO ABOUT 95% CONCENTRATION TO FORM A RAFFINATE COMPRISING STRAIGHT CHAIN OLEFINS AND AN EXTRACT COMPRISING SAID ACID AND BRANCHED CHAIN OLEFINS, SEPARATING SAID EXTRACT FROM THE RAFFINATE AND ADDING AN AROMATIC HYDROCARBON TO THE EXTRACT, SUBJECTING THE RESULTANT MIXTURE TO ALKYLATING CONDITIONS TO 